There are several potential reasons why the porphyrin count for a particular patient may not be reduced-or worse case, increase, after cleansing his/her skin. First, certain types of paper/tissue that might have been used to dry the face after cleansing could have a high content of lint particles. Lint will actually fluoresce under UV light. Greg Hillebrand, a subject matter expert at P&G on the subject, offers the further explanation that "in some situations, the true porphyrin fluorescence of an initial image could be quenched by something that the subject had on his/her unclean face, and then after removal of this interfering quenching agent, a higher level of fluorescence could be observed. Finally, the simple cleansing of the skin with a normal everyday facial cleanser is probably not going to change the true number of pores that show porphyrin fluorescence. It has been reported that washing with a cleanser containing benzoyl peroxide will, over time, reduce the number of pores. Also, using strips or other devices to physically remove the contents of the pores will help to reduce the fluorescence as well."